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In this paper we characterize $m$-isometric and quasi-$m$-isometric weighted conditional type (WCT) operators on the Hilbert space $L^2(\mu)$. Also, we prove that the subclasses of $m$-isometric and quasi-$m$-isometric of normal WCT…

Functional Analysis · Mathematics 2025-09-30 Y. Estaremi , M. S. Al Ghafri , S. Shamsigamchi

This paper establishes comprehensive stability results for quasi-variational inequalities (QVIs) under monotone perturbations of the governing operator. We prove strong convergence of both minimal and maximal solutions when sequences of…

Functional Analysis · Mathematics 2025-12-16 M. H. M. Rashid

In this paper we consider unbounded weighted conditional type operators on the space Lp, we give some conditions under which they are densely defined and we obtain a dense subset of the domain. Also, we get that a WCT operator is continuous…

Functional Analysis · Mathematics 2015-12-25 Yousef Estaremi

In this paper we are concerned with weighted conditional type(WCT) operators on Orlicz spaces. We prove that all WCT operators have finite ascent. Also, we provide some sufficient conditions for WCT operators to have finite descent. As a…

Functional Analysis · Mathematics 2023-05-17 S. Nojoumi , S. Shamsigamchi

In this paper, we give some necessary and sufficient conditions for weighted conditional expectation type operators on L2 to be centered. Also, we investigate the relation between normal and centered weighted con- ditional type operators.…

Functional Analysis · Mathematics 2014-03-07 Yousef Estaremi

We reveal new aspects of the structure of Hilbert space $C_0$-semigroups $\mathcal T = (T(t))_{t\ge 0}$ similar to semigroups of contractions. In particular, we prove that $\mathcal T$ is similar to a semigroup of contractions if and only…

Functional Analysis · Mathematics 2025-09-04 J. Oliva-Maza , Y. Tomilov

In this paper, the spectrum, residual spectrum, point spectrum and spectral radius of weighted conditional type operators are computed. As an application, we give an equivalent condition for weighted conditional type operators to be…

Functional Analysis · Mathematics 2013-10-09 Yousef Estaremi

It is known that weak l-sequential supercyclicity implies weak quasistability, and it is still unknown weather weak l-sequential supercyclicity implies weak stability, much less whether weak supercyclicity implies weak stability (although…

Functional Analysis · Mathematics 2024-12-18 C. S. Kubrusly , P. C. M. Vieira

We discuss the two closely related, but different concepts of weak and almost weak stability for the powers of a contraction on a separable Hilbert space. Extending Halmos' and Rohlin's theorems in ergodic theory as a model, we show that…

Functional Analysis · Mathematics 2008-07-21 Tanja Eisner , Andras Sereny

An absolute continuity approach to quasinormality which relates the operator in question to the spectral measure of its modulus is developed. Algebraic characterizations of some classes of operators that emerged in this context are…

Functional Analysis · Mathematics 2013-10-15 Zenon Jan Jablonski , Il Bong Jung , Jan Stochel

We prove collective versions of semi-duality theorems for sets of almost (limitedly, order) L-weakly compact operators.

Functional Analysis · Mathematics 2024-10-29 Safak Alpay , Eduard Emelyanov , Svetlana Gorokhova

This paper investigates composition operators and weighted composition operators on semi-Hilbert spaces induced by positive multiplication operators on \( L^2(\mu) \). Within the framework of \( A \)-adjoint operators, we characterize…

Functional Analysis · Mathematics 2025-08-08 Y. Estaremi , M. S. Al Ghafri

This paper introduces and investigates the class of \textit{$k$-quasi $n$-power posinormal operators} in Hilbert spaces, generalizing both posinormal and $n$-power posinormal operators. We establish fundamental properties including matrix…

Functional Analysis · Mathematics 2025-09-18 Sophiya S Dharan , T. Prasad , M. H. M. Rashid

In this paper, we present some necessary and sufficient conditions for semi-compact operators being almost L-weakly compact (resp. almost M-weakly compact) and the converse. Mainly, we prove that if $X$ is a nonzero Banach space, then every…

Functional Analysis · Mathematics 2019-04-24 Hui Li , Zili Chen

In this paper, we consider a quasi-linear Dirichlet system with possible competing $(p,q)$-Laplacians and convections. Due to the lack of ellipticity, monotonicity, and variational structure, the standard approaches to the existence of weak…

Analysis of PDEs · Mathematics 2023-05-09 L. Gambera , S. A. Marano , D. Motreanu

We study the asymptotic behaviour of contractive operators and strongly continuous semigroups on separable Hilbert spaces using the notion of rigidity. In particular, we show that a "typical" contraction $T$ contains the unit circle times…

Functional Analysis · Mathematics 2014-05-01 Tanja Eisner

We study unitarily equivalent bilateral weighted shifts with operator weights. We establish a general characterization of unitary equivalence of such shifts under the assumption that the weights are quasi-invertible. We prove that under…

Functional Analysis · Mathematics 2024-07-30 Michał Buchała

Approximation properties of multivariate quasi-projection operators are studied in the paper. Wide classes of such operators are considered, including the sampling and the Kantorovich-Kotelnikov type operators generated by different…

Classical Analysis and ODEs · Mathematics 2020-03-26 Yurii Kolomoitsev , Maria Skopina

In this paper, some various partial normality classes of weighted conditional expectation type operators on L2() are investigated. Also, some applications of weak hyponormal weighted conditional type operators are pre- sented.

Functional Analysis · Mathematics 2013-09-17 Yousef Estaremi

In a many-to-one matching model in which firms' preferences satisfy substitutability, we study the set of worker-quasi-stable matchings. Worker-quasi-stability is a relaxation of stability that allows blocking pairs involving a firm and an…

Theoretical Economics · Economics 2022-03-04 Agustin G. Bonifacio , Nadia Guinazu , Noelia Juarez , Pablo Neme , Jorge Oviedo
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